Recently, I had just read a science research article regarding the origin of the names of the planets in the universe. In my opinion, it seems like almost all planets or stars are named after either Greek or Roman gods (strange......?!). So let's take Uranus for example. Uranus, one of the planets in the solar system, is actually named after the ancient Greek deity of the sky Uranus, the father of Kronos (Saturn) and grandfather of Zeus (Jupiter).

Perhaps, Earth is also named after ancient gods. However, this seems to be wrong! The Earth is actually the only planet whose name in English is not derived from Greco-Roman mythology! According to my research, the name 'Earth' originates from the 8th century Anglo-Saxon word erda, which means ground or soil.

  

However, in my opinion, I think it's quite impossible to find out who first named the planet 'Earth'. To be frank, I'm not really an expert on words and word origins of these planets, but this seems likely that people used Earth to mean 'land' and then it was the natural thing to refer to all the land and the planet. So that's why the Earth is named 'Earth'! If I'm not wrong...... :)